Inspection systems and methods for blow-molded containers

ABSTRACT

Systems and methods for in-line inspection of plastic blow molded containers. The inspection system may comprise a plurality of emitter assemblies arranged in a vertical array. Each emitter assembly may cyclically emit light energy in at least two different narrow wavelength bands at a container as the container passes through an inspection area. The system may also comprise a plurality of broadband photodetectors arranged in a vertical array, each photodetector facing at least one of the emitter assemblies with the inspection area therebetween such that the photodetectors are capable of sensing light energy that passes through the container when it is in the inspection area. The system may also comprise a processor in communication with the photodetectors for determining a characteristic of the container based on signals from the photodetectors.

PRIORITY CLAIM

The present application is a continuation of U.S. patent applicationSer. No. 12/310,263, entitled, “In-Line Inspection System for VerticallyProfiling Plastic Containers Using Multiple Wavelength Discrete SpectralLight Sources,” by William E. Schmidt, et al., which is incorporated byreference herein in its entirety, which is the national stage of PCTapplication Serial No. PCT/US07/19230, and which claims priority to U.S.provisional application Ser. No. 60/841,954, filed Sep. 1, 2006,entitled, “Measuring container characteristics using multiple wavelengthdiscrete spectral light sources and broadband detectors,” by William E.Schmidt, et al., also incorporated herein by reference in its entirety.

BACKGROUND

Measuring characteristics of plastic bottles is well known andstandardized test methods for such exist within industry. For example,it is known to measure the wall thickness of a plastic bottle using asystem that employs a broadband light source, a chopper wheel, and aspectrometer to measure the wall thickness of the plastic bottle as itpasses between the light source and the spectrometer after being formedby a blow molder. The broadband light source in such a system provideschopped IR light energy that impinges the surface of the plasticcontainer, travels through both walls of the container, and is sensed bythe spectrometer to determine absorption levels in the plastic atdiscrete wavelengths. This information is used to determinecharacteristics of the plastic bottle, such as wall thickness. Othermachines are available from several manufacturers throughout the world.Exemplary of such machines is the AGR TopWave Petwall Plus Visionsystem. This machine performs a thickness measurement of plasticcontainers by measuring the difference between a PET absorptionwavelength and a non-absorption reference wavelength.

In practice, such systems use an incandescent bulb to generate broadbandlight within the visible and infrared spectrums of interest. Thebroadband light is chopped, collimated, transmitted through two walls ofthe plastic container, and finally divided into wavelengths of interestby the spectroscope. This sampling process is limited in both speed andresponse time.

The state of the art in blow molding technology continues to increasethe sampling speed required. This will, in time, render the currenttechnologies used to measure container characteristics unusable.

SUMMARY OF THE INVENTION

In one general aspect, the present invention is directed to aninspection system for inspecting blow molded plastic or PET(polyethylene terephthalate) containers. According to variousembodiments, the inspection system is an in-line system that comprises avertical array of emitter assemblies that cyclically emit light energyin at least two different narrow wavelength bands at a blow moldedcontainer as the container passes through an inspection area. Forexample, each emitter assembly may comprise two narrow band lightsources: one that emits light energy in a narrow wavelength band that isabsorbed by the material of the container in a manner highly dependenton the thickness of the material; and one that emits light energy inanother, discrete narrow wavelength band that is substantiallytransmissive by the material of the container. The light sources may beLEDs or laser diodes, for example.

The inspection system may also comprise a vertical array of broadbandphotodetectors facing the emitter assemblies, such as in a 1-to-1relationship. The light energy that is not absorbed by the container maypass through two sidewalls of the container, where the light energy issensed by the photodetectors. Each broadband photodetector preferablyhas a broad enough response range to detect light energy from thedifferent light sources of the emitter assemblies. The inspection systemmay also comprise a processor in communication with the photodetectors,where the processor is programmed to determine a characteristic of theinspected container, such as the average 2-wall thickness of thecontainer or some other characteristic, based on output signals from thephotodetectors. This information may be used in determining whether thecontainer should be rejected. The processor may also be programmed tocalculate real, time calibration adjustments for the emitters andsensors to maintain calibration. Further, the processor may also beprogrammed to send control signals to the blow molder system to adjustparameters of the blow molder, such as heating temperature or otherparameters, to close a feedback control loop for the blow molder system.

According to various embodiments, the light sources in the emitterassemblies may be cyclically controlled such that during each cyclethere is a time period when: only one of the light sources is on; onlythe other light source is on; and both light sources are off. Such atiming architecture may aid the processor in determining thecharacteristics of the container and for calculating the calibrationadjustments.

According to various embodiments, pairs of emitters and sensors may berelatively densely spaced along the vertical span of the containers inthe inspection area. Thus, a relatively complete thickness profile ofthe inspected container may be obtained.

These and other benefits of the invention will be apparent from thedescription to follow.

FIGURES

Various embodiments of the present invention are described herein by wayof example in conjunction with the following figures, wherein:

FIG. 1 is simplified block diagram of a blow molder system according tovarious embodiments of the present invention;

FIGS. 2, 3 and 11 provide views of a portion of an inspection systemaccording to various embodiments of the present invention;

FIGS. 4 to 8 show an emitter assembly of the inspection system accordingto various embodiments of the present invention;

FIG. 9 shows a sensor of the inspection system according to variousembodiments of the present invention;

FIG. 10 is a simplified block diagram of a sensor circuit board of theinspection system according to various embodiments of the presentinvention;

FIG. 12 is a simplified block diagram of a driver board for an emitterassembly 60 of the inspection system according to various embodiments ofthe present invention;

FIG. 13 is a timing diagram according to various embodiments of thepresent invention;

FIG. 14 is a simplified block diagram of the inspection system accordingto various embodiments of the present invention; and

FIG. 15 shows a staggered vertical array of emitter assemblies accordingto various embodiments of the present invention.

DESCRIPTION OF INVENTION

In one general aspect, the present invention is directed to aninspection system for measuring a characteristic of a container, such asa plastic, PET, or other type of polyolefin container. As describedbelow, the inspection system may comprise (1) multiple wavelengthdiscrete spectral light sources with high energy output, and (2) highlysensitive broadband detectors (or sensors). The inspection system mayalso comprise a processor to determine the characteristic (orcharacteristics) of the containers based on the light energy from thelight sources detected by the sensors. Such an inspection system may beused in plastic or PET container manufacturing operations operating athigher blow molder speeds. The wavelength discrete spectral lightsources may comprise, for example, a number of light emitting diodes(LEDs) or laser diodes, having different, narrow band emission spectra.The characteristics measured by the system based on the ratio of thelight energy absorbed by the containers at the selected wavelengthranges may include, for example, wall thickness (e.g., average 2-wallthickness) or characteristics related to wall thickness, such as mass,volume, and/or material distribution of the walls of the container. Asdescribed further below, the measured characteristics may be used toreject manufactured containers that do not meet specifications and/orfor modifying parameters of the blow molder system (e.g., temperature,pressure and/or blow timing).

Before describing the inspection system in more detail, an overview of ablow molder system in which the inspection system may be employed isprovided. FIG. 1 is a block diagram of a blow molder system 4 accordingto various embodiments of the present invention. The blow molder system4 includes a preform oven 2 that typically carries the plastic preforms,from which the containers are manufactured, on spindles through the ovensection so as to preheat the preforms prior to blow-molding of thecontainers. The preform oven 2 may comprise, for example, infraredheating lamps or other heating devices to heat the preforms above theirglass transition temperature. The preforms leaving the preform oven 2enter the blow molder 6 by means, for example, of a conventionaltransfer system 7 (shown in phantom).

The blow molder 6 may comprise a number of molds, such as on the orderof ten to twenty-four, for example, arranged in a circle and rotating ina direction indicated by the arrow C. The preforms may be stretched inthe blow molder, using air and/or a core rod, to conform the preform tothe shape defined by the mold. Containers emerging from the blow molder6, such as container 8, may be suspended from a transfer arm 10 on atransfer assembly 12, which is rotating in the direction indicated byarrow D. Similarly, transfer arms 14 and 16 may, as the transferassembly 12 rotates, pick up the container 8 and transport the containerthrough the inspection area 20, where it may be inspected by theinspection system described below. A reject area 24 has a rejectmechanism 26 that may physically remove from the transfer assembly 12any containers deemed to be rejected.

In the example of FIG. 1, container 30 has passed beyond the reject area24 and may be picked up in a star wheel mechanism 34, which is rotatingin direction E and has a plurality of pockets, such as pockets 36, 38,40, for example. A container 46 is shown in FIG. 1 as being present insuch a star wheel pocket. The containers may then be transferred in amanner known to those skilled in the art to conveyer means according tothe desired transport path and nature of the system. According tovarious embodiments, the blow molder system 4 may produce containers ata rate of 20,000 to 100,000 per hour.

FIGS. 2 and 3 illustrate an inspection system 50 according to variousembodiments of the present invention. The inspection system 50, asdescribed further below, may be an in-line inspection system thatinspects the containers as they are formed, as fast as they are formed(e.g., up to 100,00 containers per hour), without having to remove thecontainers from the processing line for inspection and without having todestroy the container for inspection. The inspection system 50 maydetermine characteristics of each container formed by the blow molder 4(e.g., average 2-wall thickness, mass, volume, and/or materialdistribution) as the formed containers are rotated through theinspection area 20 by the transfer assembly 12 following blow molding.FIG. 2 is a perspective view of the inspection system 50 and FIG. 3 is afront plan view of the inspection system 50. As shown in these figures,the inspection system 50 may comprise two vertical arms 52, 54, with across bar section 56 therebetween at the lower portion of the arms 52,54. One of the arms 52 may comprise a number of light energy emitterassemblies 60, and the other arm 54 may comprise a number of broadbandsensors 62 for detecting light energy from the emitter assemblies 60that passes through a plastic container 66 passing between the arms 52,54. Thus, light energy from the emitter assembly 60 that is not absorbedby the container may pass through the two opposite sidewalls of thecontainer 66 and be sensed by the sensors 62. The container 66 may berotated through the inspection area 20 between the arms 52, 54 by thetransfer assembly 12 (see FIG. 1). In other embodiments, a conveyor maybe used to transport the containers through the inspection area 20.

According to various embodiments, the emitter assemblies 60 may comprisea pair of light emitting diodes (LEDs) that emit light energy atdifferent, discrete narrow wavelengths bands. For example, one LED ineach emitter assembly 60 may emit light energy in a narrow bandwavelength range where the absorption characteristics of the material ofthe container are highly dependent on the thickness of the material ofthe plastic container 66 (“the absorption wavelength”). The other LEDmay emit light energy in a narrow band wavelength that is substantiallytransmissive (“the reference wavelength”) by the material of the plasticcontainer 66.

According to various embodiments, there may be one broadband sensor 62in the arm 54 for each emitter 60 in the arm 52. Based on the sensedenergy at both the absorption and reference wavelengths, the thicknessthrough two walls of the container 66 can be determined at the heightlevel of the emitter-sensor pair. This information can be used indetermining whether to reject a container because its walls do not Meetspecification (e.g., the walls are either too thin or too thick). Thisinformation can also be used as feedback for adjusting parameters of thepreform oven 2 and/or the blow molder 6 (see FIG. 1) according tovarious embodiments, as described further below.

The more closely the emitter-sensor pairs are spaced vertically, themore detailed thickness information can be obtained regarding thecontainer 66. According to various embodiments, there may be betweenthree (3) and fifty (50) such emitter-sensor pairs spanning the heightof the container 66 from top to bottom. Preferably, there are up tothirty two emitter-sensor pairs spaced every 0.5 inches or less. Suchclosely spaced emitter-sensor pairs can effectively provide a rathercomplete vertical wall thickness profile for the container 66.

According to various embodiments, when the inspection system 50 is usedto inspect plastic or PET containers 66, the absorption wavelengthnarrow band may be around 2350 nm, and the reference wavelength band maybe around 1835 nm. Of course, in other embodiments, different wavelengthbands may be used. As used herein, the terms “narrow band” or “narrowwavelength band” means a wavelength band that is less than or equal to200 nm full width at half maximum (FWHM). That is, the differencebetween the wavelengths at which the emission intensity of one of thelight sources is half its maximum intensity is less than or equal to 200nm. Preferably, the light sources have narrow bands that are 100 nm orless FWHM, and preferably are 50 nm or less FWHM.

The arms 52, 54 may comprise a frame 68 to which the emitter assemblies60 and sensors 62 are mounted. The frame 68 may be made of any suitablematerial such as, for example, aluminum. Controllers on circuit boards(not shown) for controlling/powering the emitter 60 and sensors 62 mayalso be disposed in the open spaces defined by the frame 68. Thecrossbar section 56 may be made out of the same material as the frame 68for the arms 52, 54.

The frame 68 may define a number of openings 69 aimed at the inspectionarea 20. As shown in FIG. 2, there may be an opening for each sensor 62.There may also be a corresponding opening for each emitter assembly 60.Light energy from the emitter assemblies may be directed through theircorresponding opening into the inspection area 20 and toward the sensors62 behind each opening 69.

FIG. 4 is a top plan view of an emitter assembly 60 according to variousembodiments of the present invention. The emitter assembly 60 maycomprise a first LED contained in a first LED sleeve 80, and a secondLED contained in a second LED sleeve 82 (sometimes respectively referredto as “first LED 80” and “second LED 82” for purposes of simplicity).One of the LEDs 80, 82 may emit light energy at the reference wavelengthand the other may emit light energy at the absorption wavelength.According to one embodiment, the first LED sleeve 80 may contain the LEDemitting at the absorption wavelength band and the second LED sleeve 82may contain the LED emitting at the reference wavelength band.

As shown in FIG. 4, the emitter assembly 60 may comprise a beam splitter84. The beam splitter 84 may be a dichroic beam splitter that issubstantially transmissive to the light energy from the first LED 80such that the light energy from the first LED 80 propagates toward theopening 69, and substantially reflective of the light energy from thesecond LED 82 such that the light energy from the second LED is alsodirected toward the opening 69. The assembly 60 may also comprise acovering 86 for each opening 69. The covering 86 may be substantiallytransmissive for the emitted wavelength bands of the first and secondLEDs.

A screw (not shown) through screw openings 88, 89 may be used to securethe assembly 60 to the frame 68. Pins (not shown) in pin openings 90, 91may be used to align the assembly 60 for improved optical performance.Conduit 92 may be used to contain electrical wires for the second LED82, such that the wires (not shown) for both the first and second LEDs80, 82 may attach the assembly 60 at a back portion 94 of the assembly60.

FIG. 5 provides another view of an emitter assembly 60. This figureshows the first LED 100 and the second LED 102. The light energy fromeach LED 100, 102 may be directed through a one or series of collectionand collimating lenses 104, 106, respectively, by highly reflectiveinterior walls 108 of a cylinder casing 110, 112 that respectivelyencases the LEDs and the lenses. Each LED 100, 102 may have anassociated circuit board 114, 116 or other type of substrate to whichthe LEDs 100, 102 are mounted and which provide an interface for theelectrical connections (not shown) to the LEDs 100, 102.

FIGS. 6-8 show different views of the emitter assemblies 60 according tovarious embodiments of the present invention. In FIGS. 7 and 8, onlyhalf (the lower half) of the emitter assemblies 60 are shown forillustration purposes.

FIG. 9 is a diagram of a sensor 62 according to various embodiments ofthe present invention. In the illustrated embodiment, the sensor 62includes a broadband photodetector 120 for sensing the light energy fromthe emitter assemblies 60. According to various embodiments, thephotodetector 120 may be an enhanced InGaAs photodetector. Such aphotodetector is capable of sensing a broad range of wavelengths,including the wavelength bands emitted by the emitter assemblies 60. Thesensor 62 may further comprise one or more lenses 122 for focusing theincoming light onto the photodetector 120. The detector may alsocomprise stray light baffles 124. Also, the photodetector 120 may havean associated circuit board 126 or other type of substrate to whichphotodetector 120 is mounted and which provides an interface for theelectrical connections (not shown) to the photodetector 120.

FIG. 10 is a simplified block diagram of the sensor 62 and an associatedsensor controller circuit board 134. As shown in FIG. 10, the sensor 62may further comprise a first amplifier 130 for amplifying the signalfrom the photodetector 120. The amplifier 130 may be integrated with thephotodetector 120 or on the controller circuit board 126 (see FIG. 9).The output of the amplifier 130 may then be input to another amplifier132 on the sensor circuit board 134. The sensor circuit board 134 may belocated near the sensor 62, such as in the open space in the arm 54, asshown in FIG. 11. According to various embodiments, each circuit board134 may interface with eight sensors 62 so that, for an embodimenthaving thirty two emitter-sensor pairs, there may be four such sensorcircuit boards 134 for the thirty-two sensors.

As shown in FIG. 10, the circuit board 134 may comprise ananalog-to-digital (A/D) converter 136 for converting the amplifiedanalog signals from the photodetector 120 to digital form. According tovarious embodiments, the ND converter 136 may be a 16-bit A/D converter.The output from the A/D converter 136 may be input to a fieldprogrammable gate array (FPGA) 140 or some other suitable circuit, suchas an ASIC. The circuit board 134 may communicate with a processor 142via a LVDS (low voltage differential signaling) communication link, forexample, or some other suitable connection (e.g., RS-232), using eitherserial or parallel data transmission. The processor 142 may be a digitalsignal processor or some other suitable processor for processing thesignals from the sensors 62 as described herein. The processor 142 mayhave a single or multiple cores. One processor 142 may process the datafrom each of the circuit boards 134, or there may be multipleprocessors. The processor(s) 142 may be contained, for example, in anelectrical enclosure 144 mounted under the crossbar section 68 of theinspection system 50, as shown in FIG. 11.

FIG. 12 is a simplified schematic diagram of a controller 148 for theemitter LEDs according to various embodiments. Each LED 100, 102 mayhave an associated switch 150, which may control when the LEDs are onand off. The switches 150 may be implemented as field effectortransistors (FETs), for example. An adjustable constant current source154 may drive the LEDs 100, 102. The current from the current sources154 may be adjusted to control the light intensity of the LEDs 100, 102for calibration purposes, for example. Any suitable adjustable currentsource may be used, such as a transistor current source or a currentmirror. The current sources 154 may be controlled by signals from a FPGA158 (or some other suitable programmable circuit) via adigital-to-analog (D/A) converter 160. The FPGA 158 may store values toappropriately compensate the intensity levels of the LEDs 100, 102 basedon feedback from the processor(s) 142.

According to various embodiments, the FPGA 158 may control the LEDs fornumerous emitter assemblies 60. For example, a single FPGA 158 couldcontrol eight emitter assemblies 60, each having two LEDs, as describedabove. The FPGA 158 along with the D/A converter 160, current sources154, and switches 150 for each of the eight channels could be containedon a circuit board near the emitter assemblies 60, such as in the spacedefined by the frame 68 of the arm 52, as shown in FIG. 11. For anembodiment having thirty-two emitter assemblies 60, therefore, therecould be four such controller circuit boards 148. The FPGAs 158 maycommunicate with the processor 142 in the enclosure (see FIG. 11) usinga LVDS connection or some other suitable serial or parallelcommunication link.

According to various embodiments, the LEDs 100, 102 may be switched onand off cyclically. During a time period when both LEDs 100, 102 areoff, the drive for the LEDs 100, 102 may be adjusted and/or the gain ofthe amplifiers 130, 132 on the sensor side may be adjusted to compensatefor drifts in performance and/or to otherwise keep the emitter-sensorpairs calibrated. FIG. 13 is a timing diagram showing the system timingarchitecture for a sampling cycle according to various embodiments ofthe present invention. In the illustrated embodiment, the switchingcycle has a duration of 20 microseconds, corresponding to a samplingrate of 50 kHz. Of course, in other embodiments, switching cycles havingdifferent durations could be used.

The LEDs 100, 102 of the emitter assemblies 60 preferably take less than500 nanoseconds to turn on, and the photodetectors 120 of the sensorspreferably have a response time of 500 nanoseconds or less. Further, therecovery time of the photodetectors 120 after turn off is preferably 500nanoseconds or less. As shown in the example of FIG. 13, at the start ofthe cycle (t=0), the absorption LED in every other emitter assembly 60(e.g., the “odd” ones) is turned on. Since the sensors 62 may detectlight energy from more than one emitter assembly 60, the emitterassemblies 60 may be turned on and off in banks in such a fashion. Inthe illustrated embodiment, the emitter assemblies 60 are operated ittwo banks (odd and even), although in other embodiments the emitterassemblies could be operated in more than two banks.

During the approximate time interval from t=2 to 3 microseconds, the NDconverter 136 (see FIG. 10) for each sensor 62 may latch and convert thesignal from the photodetector 120 for this condition (the odd absorptionLEDs being on). At t=3 microseconds, the odd LEDs may be turned off, andat t=4 microseconds the odd reference LEDs may be turned on. During theapproximate time interval from t=6 to 7 microseconds, the A/D converter136 for each sensor 62 may latch and convert the signal from thephotodetector 120 for the condition when the odd reference LEDs are on.At t=7 microseconds, the odd reference LEDs may then be turned off.

From t=7 microsecond to t=12 microsecond, all of the LEDs of the emitterassemblies may be turned off. During the approximate time interval fromt=10 to 11 microseconds, the A/D converter 136 for each sensor 62 maylatch and convert the signal from the photodetector 120 for thecondition when the all of the LEDs are off. At time t=12 microseconds,the “even” absorption LEDs (i.e., the ones that were not turned on att=0 microseconds) are turned on. During the approximate time intervalfrom t=14 to 15 microseconds, the A/D converter 136 for each sensor 62may latch and convert the signal from the photodetector 120 for thecondition when the even absorption LEDs are on. At t=15 microseconds theeven absorption LEDs are turned off, and at t=16 microseconds the evenreference LEDs are turned on. During the approximate time interval fromt=18 to 19 microseconds, the ND converter 136 for each sensor 62 maylatch and convert the signal from the photodetector 120 for thecondition when the even reference LEDs are on. At t=19 microseconds, theeven references LEDs are turned off. The cycle may then be repeatedstarting at t=20 microseconds, and so on.

According to various embodiments where a blow molder system (such asblow molder system 4 of FIG. 1) is used to fabricate the plasticcontainers, multiple sensors that are within or operatively associatedwith the blow molder system may provide information to a processor (suchas processor 142) to enable synchronization of the specific molds andspindles in the blow molder which made the container being inspected andthereby provide valuable feedback information. One sensor, designatedthe blow-molder machine step sensor, may emit a signal which containsinformation regarding the counting of the molds and spindles from theircorresponding starting position. The total number of molds or spindlesmay vary depending upon the make and model of blow-molder, but thisinformation is known in advance. This information may be programmed intothe system. A second signal, which is from the blow-moldersynchronization sensor, may provide information regarding start of a newcycle of rotating the mold assembly. The blow-molder spindlesynchronizing sensor provides output regarding the new cycle of rotatingthe spindle assembly. The sensors employed for monitoring machine stepmold sync and spindle sync may be positioned at any suitable locationwithin the blow-molder and may be of any suitable type, such asinductive sensors which are well known to those skilled in the art.

A part-in-place sensor may provide a signal to the processor(s) 142indicating that a container has arrived at the inspection system 20 andthat the light-energy-based inspection should be initiated. At thatpoint, the container transects the beams of emitted light from themultiple discrete-wavelength spectral light sources 60. The processor(s)142 is in communication with the broadband sensors 62 and receiveselectrical signals from the sensors 62, as described above, in order toperform a comparison of the thickness information contained within theelectrical signals with stored information regarding desired thickness.More details regarding such sensors are described in U.S. Pat. No.6,863,860, which is incorporated herein by reference.

According to various embodiments, if the thickness is not within thedesired range, the processor(s) 142 may emits a signal or command to ablow-molder reject mechanism 26, which in turn initiates a rejectionsignal to operate a container rejection system and discard thatcontainer from the conveyer.

FIG. 14 is a diagram illustrating the processor-based control systemthat may be realized using the inspection system 50 according to variousembodiments. The signals from the photodetectors 120/sensor circuitboards 134 are input to the processor 142, including the signals for theconditions when only the absorption LEDs are on, when only the referenceLEDs are on, and when all of the LEDs are off. Based on thisinformation, the processor 142 can compute or determine the averagethickness through 2 sidewalls of the container 66 at each height levelof the emitter-sensor pairs. Thus, for example, if there are thirty-twoemitter-sensor pairs, the processor 142 can compute the averagethickness through 2 sidewalls of the container 66 at thirty-twodifferent height levels on the bottle. This information can be used todetermine if a container should be rejected. If a container is to berejected, the processor 142 may be programmed to send a reject signal tothe reject mechanism 26 to the cause the container to be rejected.

The processor 142 could also compute the mass, volume and/or materialdistribution of the container as these attributes (or characteristics)are related to thickness. The mass or volume of various sections of theinspected container, e.g., sections corresponding to the various heightlevels of the emitter-sensor pair, could also be calculated by theprocessor. The processor could also compute container diameter bymeasuring the time between detection of the leading edge of thecontainer and detection of the trailing edge. This time interval, whencombined with container velocity information, provides an indication ofcontainer diameter at multiple elevations, sufficient for identificationof malformed containers.

The processor 142 may be programmed to also calculate trendinginformation, such as the average thickness at each height level for thelast x containers and/or the last y seconds. Also, other relevant,related statistical information (e.g., standard deviation, etc.) couldbe calculated. Based on this information, the processor 142 may beprogrammed to, for example, send a control signal to the preform oven 2to modify the temperature of its heaters (e.g., raise or lower thetemperature).

The processor 142 may be programmed to also calculate updatedcalibration data for the emitter assemblies 60 and the sensors 62 basedon the signals from the sensor circuit boards 134. For example, theprocessor 142 may be programmed to compute whether the drive signal fromthe current sources 154 for the emitter assemblies 60 must be adjustedand/or whether the gain of either of the amplifier stages 130, 132 ofthe sensor circuit board 134 must be adjusted. The processor 142 may beprogrammed to transmit the calibration adjustment signals to one or moreof the FPGAs 158 of the driver boards 148 for the emitter assemblies 60and, based on calibration values coded into the FPGAs 158, the FPGAs 158may control the drive signal from the current source 154. Similarly, theprocessor may transmit calibration adjustment signals to the FPGAs 140of the sensor circuit boards 134 and, based on calibration values codedinto the FPGAs 140, the FPGAs 140 may control the gain of the amplifierstages 130, 132 to maintain calibration.

Also, based on the mold-spindle timing sensor information from the blowmolder 6, as described above, the processor 142 could calculate theaverage thickness at each height level for the last x containers for aspecified mold, spindle, and/or mold-spindle combination. The processor142 could also calculate other related statistical information that maybe relevant. This information may be used to detect a defective mold orspindle, or to adjust a parameter of the blow molder 6.

The system may also include, in some embodiments, a vision system 200for inspecting the formed containers. The vision system 200 may compriseone or more cameras to capture images of the formed containers eitherfrom the top, bottom, and/or sides. These images may be passed to theprocessor 142 and analyzed to detect defects in the formed containers.If a container with defects is detected, the processor 142 may beprogrammed to send a signal to the reject mechanism to reject thecontainer. The vision system could be similar to the vision system usedin the AGR TopWave PetWall Plus thickness monitoring system or asdescribed in U.S. Pat. No. 6,967,716, which is incorporated herein byreference.

The output thickness information from the processor(s) 142, as well asthe vision-based information for a system that includes a vision system200, may be delivered to a graphical user interface 202, such as a touchscreen display. The GUI 202 may provide an operator with informationregarding specific containers produced by particular mold and spindlecombinations of the blow molder. It is preferred that the values beaveraged over a period of time, such as a number of seconds or minutes.In addition or in lieu of time measurement, the average may be obtainedfor a fixed number of containers which may be on the order of 2 to 2500.The GUI 202 may also provide trend information for the blow-molder andindividual molds and spindles. In the event of serious problemsrequiring immediate attention, visual and/or audio alarms may beprovided. In addition, the operator may input certain information to theprocessor 142 via the GUI 202 to alter calibrations in order to controloperation of the processor(s). Also, the operator may input processlimits and reject limits into the processor(s) 142 for each of thethickness measurement zones of the containers to be inspected. Thereject limits are the upper and lower thickness values that wouldtrigger the rejection of a container. The process limits are the upperand lower values for the time-averaged or number of container averagedthickness that would trigger a process alarm indicator.

According to various embodiments, in addition to or in lieu of LEDs, thelight emitter assemblies 60 may use one or more laser diodes to emitlight energy at the discrete wavelength bands. Also, instead of adichroic beam splitter 84 in the emitter assemblies 60 to merge thediscrete narrow band light sources, other optical techniques could beused to achieve the same effect. For instance, a bifurcated fiber opticcoupler may used to mix the light energy from the two discrete lightsources.

Although the preferred embodiment uses enhanced InGaAs photodetectors120, in other embodiments other types of detectors could be used to thesame effect. For instance, PbS detectors could be used to measure abroad range of light in the relevant wavelength ranges. In addition,although the above-described embodiments use vertically aligned LEDs andsensors, an alternative configuration would stagger the mounting ofadjacent LEDs/sensor pairs in order to achieve a more densely stackedvertical array of sensors, as shown in the example of FIG. 15, whichjust shows a staggered vertical array of emitter assemblies 60. Invarious embodiments, the photodetectors could be similarly staggered.

The examples presented herein are intended to illustrate potential andspecific implementations of the embodiments. It can be appreciated thatthe exemplary embodiments are intended primarily for purposes ofillustration for those skilled in the art. No particular aspect oraspects of the examples is/are intended to limit the scope of thedescribed embodiments.

As used in the claims, the term “plastic container(s)” means any type ofcontainer made from any type of plastic material including polyvinylchloride, polyethylene, polymethyl methacrylate, polyurethanes,thermoplastic, elastomer, PET, or polyolefin, unless otherwisespecifically noted.

It is to be understood that the figures and descriptions of theembodiments have been simplified to illustrate elements that arerelevant for a clear understanding of the embodiments, whileeliminating, for purposes of clarity, other elements. For example,certain operating system details and power supply-related components arenot described herein. Those of ordinary skill in the art will recognize,however, that these and other elements may be desirable in inspectionsystems as described hereinabove. However, because such elements arewell known in the art and because they do not facilitate a betterunderstanding of the embodiments, a discussion of such elements is notprovided herein.

In general, it will be apparent to one of ordinary skill in the art thatat least some of the embodiments described herein may be implemented inmany different embodiments of software, firmware and/or hardware. Thesoftware and firmware code may be executed by a processor (such as theprocessor 142) or any other similar computing device. The software codeor specialized control hardware which may be used to implementembodiments is not limiting. The processors and other programmablecomponents disclosed herein may include memory for storing certainsoftware applications used in obtaining, processing and communicatinginformation. It can be appreciated that such memory may be internal orexternal with respect to operation of the disclosed embodiments. Thememory may also include any means for storing software, including a harddisk, an optical disk, floppy disk, ROM (read only memory), RAM (randomaccess memory), PROM (programmable ROM), EEPROM (electrically erasablePROM) and/or other computer-readable media.

In various embodiments disclosed herein, a single component may bereplaced by multiple components and multiple components may be replacedby a single component, to perform a given function or functions. Exceptwhere such substitution would not be operative, such substitution iswithin the intended scope of the embodiments. For example, processor 142may be replaced with multiple processors.

While various embodiments have been described herein, it should beapparent that various modifications, alterations and adaptations tothose embodiments may occur to persons skilled in the art withattainment of at least some of the advantages. The disclosed embodimentsare therefore intended to include all such modifications, alterationsand adaptations without departing from the scope of the embodiments asset forth herein.

1. An inspection system for inspecting blow molded plastic containerscomprising: a plurality of emitter assemblies arranged in a verticalarray, wherein the emitter assemblies cyclically emit light energy in atleast two different narrow wavelength bands at a blow molded plasticcontainer as the container passes through an inspection area; aplurality of broadband photodetectors arranged in a vertical array, eachphotodetector facing at least one of the emitter assemblies such thatthe photodetectors are capable of sensing light energy that passesthrough the container when it is in the inspection area; and a processorin communication with the photodetectors for determining acharacteristic of the container based on signals from thephotodetectors.
 2. The inspection system of claim 1, wherein the signalsfrom the photodetectors are indicative of the amount of light absorbedby the container at both of the at least two different narrow wavelengthbands.
 3. The inspection system of claim 2, wherein the characteristiccomprises the two-wall average thickness of the container at each heightlevel of the plurality of photodetectors.
 4. The inspection system ofclaim 2, wherein the characteristic comprises a characteristic selectedfrom the group consisting of mass and volume.
 5. The inspection systemof claim 1, further comprising: a first vertical arm, wherein theplurality of emitter assemblies are mounted in the first vertical arm;and a second vertical arm, wherein the plurality of photodetectors aremounted in the second vertical arm.
 6. The inspection system of claim 5,wherein the number of emitter assemblies equals the number ofphotodetectors.
 7. The inspection system of claim 6, wherein the emitterassemblies are vertically aligned and the photodetectors are verticallyaligned.
 8. The inspection system of claim 1, wherein each emitterassembly comprises: a first light source that emits light energy in afirst narrow wavelength band; and a second light source that emits lightenergy in a second narrow wavelength band that is different from thefirst narrow wavelength band.
 9. The inspection system of claim 8,wherein the inspection system further comprises a controller incommunication with at least a first emitter assembly, wherein thecontroller is for controlling the first of the emitter assembly suchthat: during a first portion of a cycle the first light source of thefirst emitter assembly is on, the second light source of the firstemitter assembly is off; during a second portion of the cycle the firstlight source is off and the second light source is on; and during athird portion of the cycle the first light source is off and the secondlight source is off.
 10. The inspection system of claim 8, wherein theinspection system further comprises a controller in communication withat least first and second emitter assemblies, wherein the controller isfor controlling the first and second emitter assemblies such that:during a first portion of a cycle the first light source of the firstemitter assembly is on, the second light source of the first emitterassembly is off, and the first and second light sources of the secondemitter assembly are off; during a second portion of a cycle the firstlight source of the first emitter assembly is off, the second lightsource of the first emitter assembly is on, and the first and secondlight sources of the second emitter assembly are off; during a thirdportion of a cycle the first and second light sources of the firstemitter assembly are off, the first light source of the second emitterassembly is on, and the second light source of the second emitterassembly is off; during a fourth portion of a cycle the first and secondlight sources of the first emitter assembly are off, the first lightsource of the second emitter assembly is off, and the second lightsource of the second emitter assembly is on; and during a fifth portionof a cycle the first and second light sources of the first emitterassembly are off, and the first and second light sources of the secondemitter assembly are off.
 11. The inspection system of claim 8, wherein:The first light source comprises a LED; and The second light sourcecomprises a LED.
 12. The inspection system of claim 8, wherein: Thefirst light source comprises a laser diode; and The second light sourcecomprises a laser diode.
 13. The inspection system of claim 8, furthercomprising: a first controller, in communication with the processor, forcontrolling at least one of the emitter assemblies; and a secondcontroller, in communication with the processor, for controlling atleast one of the broadband photodetectors, and wherein the processor isprogrammed to communicate calibration adjustments to the first andsecond controllers.
 14. The inspection system of claim 1, wherein atleast one of the plurality of broadband photodetectors comprises anInGaAs photodetector.
 15. The inspection system of claim 8, wherein eachof the emitter assemblies comprise a beam splitter.
 16. A blow moldingsystem for blow molding plastic containers from preforms, the systemcomprising: an oven for heating the preforms; a blow molder for moldingthe heated preforms into the plastic containers; and an in-lineinspection system for inspecting the plastic containers as they areformed by the blow molder, wherein the inspection system comprises: aplurality of emitter assemblies that cyclically emit light energy in atleast two different narrow wavelength bands at a container as thecontainer passes through an inspection area; a plurality of broadbandphotodetectors, each photodetector facing at least one of the emitterassemblies such that photodetectors are capable of sensing light energythat passes through the container when it is in the inspection area; anda processor in communication with the photodetectors for determining acharacteristic of the container based on signals from thephotodetectors.
 17. The blow molding system of claim 16, wherein thesignals from the photodetectors are indicative of the amount of lightabsorbed by the container at both of the at least two different narrowwavelength bands.
 18. The blow molding system of claim 16, wherein theinspection system further comprises: a first vertical arm, wherein theplurality of emitter assemblies are vertically aligned in the firstvertical arm; and a second vertical arm, wherein the plurality ofphotodetectors are vertically aligned in the second vertical arm. 19.The blow molding system of claim 16, wherein each emitter assemblycomprises: a first light source that emits light energy in a firstnarrow wavelength band; and a second light source that emits lightenergy in a second narrow wavelength band that is different from thefirst narrow wavelength band.
 20. The blow molding system of claim 19,wherein the inspection system further comprises a controller incommunication with at least a first emitter assembly, wherein thecontroller is for controlling the first emitter assembly such that:during a first portion of a cycle the first light source of the firstemitter assembly is on, the second light source of the first emitterassembly is off; during a second portion of the cycle the first lightsource is off and the second light source is on; and during a thirdportion of the cycle the first light source is off and the second lightsource is off.
 21. The blow molding system of claim 19, wherein theinspection system further comprises a controller in communication withat least first and second emitter assemblies, wherein the controller isfor controlling the first and second emitter assemblies such that:during a first portion of a cycle the first light source of the firstemitter assembly is on, the second light source of the first emitterassembly is off, and the first and second light sources of the secondemitter assembly are off; during a second portion of a cycle the firstlight source of the first emitter assembly is off, the second lightsource of the first emitter assembly is on, and the first and secondlight sources of the second emitter assembly are off; during a thirdportion of a cycle the first and second light sources of the firstemitter assembly are off, the first light source of the second emitterassembly is on, and the second light source of the second emitterassembly is off; during a fourth portion of a cycle the first and secondlight sources of the first emitter assembly are off, the first lightsource of the second emitter assembly is off, and the second lightsource of the second emitter assembly is on; and during a fifth portionof a cycle the first and second light sources of the first emitterassembly are off, and the first and second light sources of the secondemitter assembly are off.
 22. The blow molding system of claim 19,further comprising: a first controller, in communication with theprocessor, for controlling at least one of the emitter assemblies; and asecond controller, in communication with the processor, for controllingat least one of the broadband photodetectors, and wherein the processoris programmed to communicate calibration adjustments to the first andsecond controllers.
 23. The blow molding system of claim 19, wherein theprocessor is further programmed to send a control signal to the oven tochange a parameter of the oven based on the characteristic determined bythe processor.
 24. The blow molding system of claim 19, wherein theprocessor is further programmed to send a control signal to the blowmolder to change a parameter of the blow molder based on thecharacteristic determined by the processor.
 25. A method of inspectingblow molded plastic containers comprising: cyclically directing lightenergy at two discrete narrow wavelength bands from a plurality ofemitter assemblies arranged in a vertical array at a blow molded plasticcontainer from an exterior of the plastic container; sensing, with aplurality of broadband photodetectors arranged in a vertical array,light energy at each of the two discrete narrow wavelength bands fromthe emitter assemblies that pass through the plastic container when theplastic container is in an inspection area between the emitterassemblies and the photodetectors; determining, based on the sensedlight energy, a characteristic of the plastic container.
 26. The methodof claim 25, wherein each emitter assembly comprises: a first lightsource that emits light energy in a first narrow wavelength band; and asecond light source that emits light energy in a second narrowwavelength band that is different from the first narrow wavelength band.27. The method of claim 26, wherein cyclically directing light energycomprises: during a first portion of a cycle, directing light energyfrom the first light source of a first portion of the emitter assemblieswhile the second light source of the first portion of the emitterassemblies is off, and the first and second light sources of a secondportion of the emitter assemblies are off; during a second portion ofthe cycle, directing light energy from the second light source of thefirst portion of the emitter assemblies while the first light source ofthe first portion of the emitter assemblies is off, and the first andsecond light sources of the second portion of the emitter assemblies areoff; during a third portion of the cycle, directing light from the firstlight source of the second portion of the emitter assemblies while thesecond light source of the second portion of the emitter assemblies isoff, and the first and second light sources of the first portion of theemitter assemblies are off; during a fourth portion of the cycle,directing light from the second light source of the second portion ofthe emitter assemblies while the first light source of the secondportion of the emitter assemblies is off, and the first and second lightsources of the first portion of the emitter assemblies are off; andduring a fifth portion of the cycle, the first and second light sourcesof the first portion of the emitter assemblies are off and the first andsecond light sources of the second portion of the emitter assemblies areoff.
 28. The method of claim 25, further comprising making calibrationadjustments to at least one of the emitter assemblies or at least one ofthe photodetectors during a cycle.
 29. A method of manufacturing aplastic container comprising: heating a preform with a preform oven;forming the plastic container from the heated preform in a blow molder;inspecting the plastic container after formation by the blow molder,wherein inspecting the plastic container comprises: cyclically directinglight energy at two discrete narrow wavelength bands from a plurality ofemitter assemblies arranged in a vertical array at the plastic containerfrom an exterior of the plastic container; sensing, with a plurality ofbroadband photodetectors arranged in a vertical array, light energy ateach of the two discrete narrow wavelength bands from the emitterassemblies that pass through the plastic container when the plasticcontainer is in an inspection area between the emitter assemblies andthe photodetectors; determining, based on the sensed light energy, acharacteristic of the plastic container.
 30. The method of claim 29,further comprising adjusting a parameter of the preform oven based onthe determined characteristic.
 31. The method of claim 29, furthercomprising adjusting a parameter of the blow molder based on thedetermined characteristic.